1. Field of the Invention
The present invention relates to a lens control device and a lens control method that cause movement of a lens in an optical axis direction using a stepping motor.
2. Description of the Related Art
Conventionally, in an imaging apparatus or the like, a stepping motor is used to move a lens in an optical axis direction. A stepping motor has a drive shaft that is rotated in accordance with a number of drive pulses that have been input, with a number of drive pulses corresponding to a distance to a drive target position being applied to the stepping motor to move the lens to the target position.
In this way, conventionally, lens drive is carried out using open loop control that uses a stepping motor. However, in a stepping motor a rotational position of a rotational axis of the motor with respect to an excitation position of the motor does not have a linear relationship, due to the effects of detent torque, which is an inherent load torque, variation in movement load etc., and an offset between the two may sometimes arise. In order to resolve this situation, improvement to drive control precision using closed loop control has been proposed (refer, for example, to Japanese patent publication No. 2013-025268 (hereafter referred to as patent publication 1)).
The closed loop control of a drive control unit such as shown in patent publication 1 requires drive current correction processing, and as well as the structure of this processing becoming complicated, processing takes up a lot of time.